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User blog:SilentShadow87/What Makes an EF5 an EF5?
Since we're trying to clean the wiki up a bit, and deleting tornadoes that users have rated EF5 without any explanation (which is understandable, who wouldn't want to have an EF5 in their hypothetical outbreak?) I thought I'd make a tutorial post explaining to new users what exactly gives a tornado an EF5 rating. Under the current Enhanced Fujita scale, there are several criteria which can be used in an EF5 rating (although none of them qualify an EF5 rating on their own; there usually need to be at least three). #Well-constructed and anchor-bolted houses are cleanly swept away. #Multi-story buildings are demolished or severely damaged. #Cars and trucks are thrown more than 300 feet/90 meters and severely mangled #Trees are completely debarked and often stripped of their branches #Deep and/or widespread ground scouring and removal of grass or crops #Highly visible wind-rowing and fine granulation of debris #High fatality-to-injury ratios #"Incredible Phenomena" Well-built houses swept away This one is actually a bit tricky, because a swept-away house doesn't necessarily mean EF5 damage on its own. The house needs to be a) well-built and b) anchor-bolted to its foundation instead of being anchored with nails or rods. Also, if the foundation is bare but debris has been pushed off the foundation and left in a pile right next to it, that's high-end EF4 damage (although sometimes the debris from houses gets mixed together, confusing the issue). If the house has a basement, another thing to look for is the appearance of the basement walls. If the basement walls at the point where the house was swept away look uneven and rough, it might not be EF5 damage without context (i.e. other EF5 damage indicators nearby); the "signature" of an EF5 being that the basement walls are left clean. To the left you can see a photo of EF5 damage from the Moore, Oklahoma tornado on May 20, 2013. (The debris seen on the left side of the photo came from another building, not the one in the photo). Multi-story buildings demolished or severely damaged If a building 4 stories high or bigger is demolished or heavily damaged, that's a good indicator of a very violent tornado, probably EF5. Brick buildings can be demolished or completely leveled, while concrete and steel buildings, like the St. John's Regional Medical Center hospital in Joplin, Missouri, have interior walls demolished, ceilings collapsed or torn out, and roofing loss. No EF5 tornado, under the Enhanced Fujita scale, has ever hit a skyscraper, but the expected damage involves the building being completely stripped of its glass with the steel framework warped and twisted, and possibly shifted slightly off of its foundation. Tim Marshall supposedly said in an interview that an extreme "super-tornado" could, theoretically, twist a glass and steel skyscraper off its foundation and topple it. On the right is a photo of EF5 damage to St. John's Regional Medical Center in Joplin, Missouri from the May 22, 2011 tornado. Cars and trucks thrown and mangled This is another complicated one, since both the distance a car or truck is thrown and how severely mangled it is are taken into account for the rating. To make matters worse, the standards for what qualifies each level of rating aren't agreed upon between NWS offices. Vehicle damage that qualifies an EF5 rating in one area might only qualify an EF4 or even EF3 rating in another area, depending on the NWS office responsible for the surveying. But, as a general rule, the farther a vehicle is thrown and the more heavily mangled it is, the higher the rating. Usually if a car or truck is thrown more than 0.5 miles (805 meters, 880 yards), a rating of EF5 is assigned, but not always. If a vehicle is thrown 200-800 yards (183-732 m), an EF5 rating is also possible based on other damage indicators. Another factor to consider is how heavily the vehicle is mangled. If a car or truck is tossed more than 200 yards but is still fairly intact when found, the damage is most likely in the EF3-EF4 range. An example of this would be the Twistex Cobalt: it was tossed about 250 yards, but was still recognizable when it was found. EF5 tornadoes can crumple cars and trucks into tight balls just a few feet (about 1 meter) across, strip away parts and leave only the frames remaining, leave them wrapped around other objects like crumpled tissue paper, or even tear them apart and wind-row the debris long distances (as seen in the case of the May 27, 1997 Jarrell, Texas tornado). On the upper left is a photo of a 20,000 pound (9.07 metric tonne) oil tanker truck that was tossed over 1 mile (1.6 km) by the May 24, 2011 El Reno, Oklahoma tornado. On the lower right is a car that was reduced to a twisted and crumpled heap by the same tornado. Debarking of trees Debarking of trees is a good sign of a violent tornado, but partial debarking can occur in moderately strong tornadoes as well. A higher-end EF2 tornado can sometimes remove patches of bark from the upper branches of trees, and strong EF3 tornadoes can and often do debark large sections of tree trunks. If, on the other hand, a tree is completely debarked, and especially if the debarked tree is also missing most or all of its branches, that points pretty strongly towards an EF5 tornado. Softwood trees like pine, spruce, fir, and other conifers are more easily debarked than hardwood trees like maple, ash, birch, oak, and mesquite. The complete debarking of a softwood tree is more likely EF3 to EF4-level damage. The debarking of young hardwood trees is not necessarily EF5 damage either. EF5 tornadoes usually completely remove all or nearly all of the bark from even the sturdiest trees, and often snap away their branches as well. Sometimes the tree is snapped off at the base and tossed, and sometimes some or most of the tree can be sheared away like a pencil in a massive sharpener, leaving only small stubs or cones behind. Smaller shrubs and hedges can be ripped apart with even the fragments debarked, and twigs and branches of trees are sometimes speared into the ground. It should be noted that on its own, tree damage can give a tornado a maximum rating of EF4. Extreme tree damage is considered a contextual support for EF5 structural damage. To the left is extreme tree damage from the April 24, 2010 Yazoo City, Mississippi tornado. On the ground is a tree that has been broken into pieces. Two of the three trees that are still standing have been reduced to completely debarked trunks. While the Yazoo City tornado was "only" rated EF4, EF5 structural damage would almost certainly have taken place in the area pictured. Notice that the tree in the middle distance appears to have suffered low-end EF3 damage. The highest winds in a tornado are often in very small and short-lived suction vortices.